In virtual colonography, either MR colonography or CT colonography, lesions are searched for either by “leafing through” 2-dimensional images, so-called MPRs, or via a virtual flight through the colon. A combination of the two methods is also frequently used. Suspect structures (=lesions) are then examined more accurately and in the case of a positive result they are appropriately marked and described more accurately in a report. This process is carried out manually, mostly by a doctor with appropriate training.
In parallel therewith, a computer-aided search (computer aided detection, CAD) is carried out in which lesions are detected, for example via a preprogrammed pattern recognition method, if appropriate with the aid of further programmed additional criteria, and likewise marked. These lesions detected with computer assistance must subsequently be reconfirmed again by the doctor in order to ensure on the one hand that no lesions are overlooked, but on the other hand lesions detected by the computer are also to be confirmed by the doctor and are to lead to a therapy only in the case of a positive result.